The Leutascher Ache is a left tributary of the River Isar in Austria.
It originates in the Tyrolean valley of Gaistal as a tailwater of the Igelsee, flows between the Wetterstein range and the Mieming Mountains, swings northeast near Leutasch, runs through the Leutaschtal, a high valley, and discharges into the Isar after passing through the Leutasch Gorge near Mittenwald in Bavaria.